1. Field of the Invention
The invention relates to novel molybdenum dialkyldithiocarbamate compositions with improved oil solubility.
2. Discussion of the Prior Art
Molybdenum dialkyldithiocarbamate (MoDTC) compositions of formula (1) wherein R1 to R4 are isotridecyl groups or mixtures of C11-C14 isoalkyl groups, and X represents oxygen and/or sulfur atoms, are well-known lubricant additives that impart antifriction, antiwear and antioxidant properties:

While MoDTC compositions of formula (1) have excellent antifriction, antiwear and antioxidant properties, they are known to lack oil solubility in high viscosity index oils and/or at lower temperatures, resulting in the formation of a haze, cloudiness or precipitate, which reduces lubricant effectiveness. For example in U.S. Pat. Nos. 5,627,146 and 6,245,725, Tanaka et al. teaches that MoDTC composition produced using di-2-ethylhexylamine and di-isotridecylamine (DTDA) have significantly improved oil solubility over MoDTC compositions produced from just DTDA.
In the disclosure herein, the inventors have surprisingly discovered MoDTC compositions with improved oil solubility can be produced from particular DTDA compositions. Specifically, the inventors found that MoDTC compositions produced from DTDA derived from oligomerization of butylene feedstocks composed of major amount (>50%) of 2-butylene and minor amounts of 1-butylene and/or isobutylene, and as a result of which have on average greater than 98% of C13 present as the constituent R groups, have improved oil solubility in high viscosity index oils and/or at lower temperatures over MoDTC compositions produced from other DTDA compositions known in the art, in particular di-C11-14-isoalkyl, C13-rich amines; and bis(C11-C14, branched and linear alkyl)amines. It should be noted that in this art di-C11-14-isoalkyl, C13-rich amines; and bis(C11-C14, branched and linear alkyl)amines are also commonly, though inaccurately, referred to as DTDA, and have on average no more than 73% of C13 present as the constituent R groups.